Automotive headlights typically have a low beam and a high beam. Low beam may also be known as dipped beam, passing beam, or meeting beam. Low beam headlamps provide a distribution of light designed to provide adequate forward and lateral illumination with limits on light directed towards the eyes of other road users, to control glare. This beam is intended for use when other vehicles are present ahead. The international ECE Regulations for filament headlamps and for high-intensity discharge headlamps specify a beam with a sharp, asymmetric cutoff preventing significant amounts of light from being cast into the eyes of drivers of preceding or oncoming cars. Control of glare is less strict in the North American SAE beam standard contained in FMVSS/CMVSS 108. High beam may also be known as main beam, driving beam, or full beam. High beam headlamps provide a bright, center-weighted distribution of light with no particular control of light directed towards other road users' eyes. As such, they are only suitable for use when alone on the road, as the glare they produce will distract other drivers. International ECE Regulations permit higher-intensity high-beam headlamps than are allowed under North American regulations. FIG. 11 shows an illustration of low beam light pattern on the ground whereas FIG. 12 shows an illustration of high beam light pattern on the ground.
The majority of today's automotive headlights use traditional light sources such as tungsten-halogen or xenon bulbs. These light sources are not as efficient as some current lighting technologies. Automotive headlights using traditional light sources, such as tungsten-halogen or xenon also suffer from short life and susceptibility to damage and failure from shock and vibration.
Furthermore, most light sources emit light in a spherical pattern. As a result, previous headlight designs created the sharp beam cutoff by projecting the image of a mechanical shutter. This method of using a mechanical shutter to block light results in wasted light since the mechanical shutter absorbs or reflects light.